Morphology-controlled Synthesis Of Rare Earth Doped YVO₄Powders By The Precipitation Method And Their Luminescent Properties

This paper describes the basic principle of photoluminescence. Thecharacteristics, photoluminescence theory and preparation methods of rare earthluminescent materials are also described. The progress and the application of rareearth luminescent materials are summarized, too.Y_1-x-yVO₄:Eu_x³⁺,Bi_y³⁺（x=0.03,0.06,0.12,0.15; y=0.03,0.05,0.06,0.09,0.12,0.15） phosphors were synthesized by the precipitation method. The structure andmorphology of the products were characterized by XRD, FE-SEM and TEM,respectively. The exitation and emission spectra of the products were investigated byfluorescence spectrometer. The XRD patterns showed that the powder was YVO₄phase with a body-centred tetragonal structure. The SEM and TEM images showedthat the YVO₄:Eu³⁺,Bi³⁺particles were spindle in shape with a major diameter of250nm and a minor one of100nm, and that the samples have polycrystallinestructure. In the excitation spectra of YVO₄:Eu³⁺,Bi³⁺powders, the broad excitationband at225³60nm wavelength range is a charge transfer transition band of O2-V5+.Narrow excitation band at370⁴20nm is attributed to characteristic transitions4f-4ffrom Eu³⁺. The excitation intensity increased with the increase of Eu³⁺concentration.The emission spectra of YVO₄:Eu³⁺,Bi³⁺phosphors have several emission peakscorresponding to the⁵D₀â†'⁷F₁（596nm） and⁵D₀â†'⁷F₂（617nm,621nm） transitions ofEu³⁺. The effect of Eu³⁺concentration on the emission intensity of YVO₄:Eu³⁺,Bi³⁺was investigated, and the results showed that the emission intensity increased with the increase of Eu³⁺first, reaching a maximum at12（mol）%of Eu³⁺, and thendecreases with increasing the Eu-doped concentration. This indicates theconcentration quenching effect for the luminescence of Eu³⁺in YVO₄host. It wasalso found that Bi³⁺could increase the emission intensity of Eu³⁺, reaching amaximum value at5（mol）%of Bi³⁺.Y_1-xVO₄:Tb_x³⁺（x=0.03,0.06,0.09,0.12,0.15,0.18,0.21） phosphors weresynthesized by the precipitation method. The structure and morphology of theproducts were characterized by XRD and FE-SEM, respectively. The exitation andemission spectra of the products were investigated by fluorescence spectrometer.The XRD patterns showed that the powder was YVO₄phase with a body-centredtetragonal structure. The SEM images showed that the YVO₄:Tb³⁺particles werespindle in shape with a major diameter of200nm and a minor one of100nm. In theexcitation spectra of YVO₄:Tb³⁺, the broad excitation band at300³50nmwavelength range is a charge transfer transition band of O2-V5+. Narrow excitationband at350⁴50nm is attributed to characteristic transitions4f⁸â†'4f⁷5d¹from Tb³⁺.The excitation intensity increased with the increase of Tb³⁺concentration. Theemission spectra of YVO₄:Tb³⁺phosphors have several emission peakscorresponding to the⁵D₃â†'⁷F₃（450nm）,⁵D₃â†'⁷F₂（468nm）,⁵D₄â†'⁷F₆（490nm） and⁵D₄â†'⁷F₅（546nm） transitions of Tb³⁺. The effect of Tb³⁺concentration on theemission intensity of YVO₄:Tb³⁺was investigated, and the results showed that theemission intensity increases with the increase of Tb³⁺first, reaching a maximum at9（mol）%of Tb³⁺, and then decreases with increasing the Tb-doped concentration.This indicates the concentration quenching effect for the luminescence of Tb³⁺inYVO₄host.